1. Field of the Invention
The present invention generally relates to an optical information recording, and, also, the present invention relates to optical information recording to be performed on an optical disk media, such as DVD-R (Digital Video or Versatile Disk, Recordable), a DVD-RW (ReWriteable), or the like, having compatibility in format with DVD media such as DVD, DVD-ROM of read-only type.
2. Description of the Related Art
A single pulse recording manner as shown in FIGS. 4C and 4D using such a light-emission waveform of an LD (Laser Diode) which is a light source to be applied to an optical disk is used as a general record waveform for CD-R. According to the recording manner, a recording power level which may have two values, or modify a rear edge of a heating pulse for the shortest data length, and, thereby, attains mark edge (PWM) recording. Information is given to both edges of the record mark according to such a PWM recording manner.
However, when this single pulse recording manner as shown in FIG. 4C is used as a recording waveform in a large data recording on a DVD-R, etc., since a record mark may include a distortion into a shape like a tear due to heat storage, or the edge may shift according to a data length, remarkably, as shown in FIG. 4D. Thereby, it may be difficult to provide a non-problematic jitter characteristic according to the single pulse recording manner.
For this reason, a multi-pulse recording manner as shown in FIGS. 9C and 9D employing such a light-emission waveform from an LD which is a light source of the laser to be applied to an optical disk may be used. Thereby, the duty of the heating pulses is adjusted, and, as a result, a proper recording power can be applied such as to result in record marks as shown in FIG. 9D, in which the influence of heat storage may be easily eliminated, and edge shift at both edges of a record mark can be effectively reduced.
However, when performing data recording according to the above-described single pulse recording manner, it is possible to know the formation state of a mark during recording by detecting the luminous energy of light reflected by the optical disk as a light-receiving signal waveform shown in FIG. 4E for a single pulse interval.
Therefore, even when recording is made while the recording power changes, the signal which shows a change in luminous energy of reflected light can be obtained. Thereby, data record can be performed with controlling to correct deviation of the recording power occurring due to LD power fluctuation, tilt error, media sensitivity unevenness, etc., in accordance with the state of this change in the luminous energy thus detected. Such a control scheme is generally referred to as an R-OPC (Running-Optimum Power Control) scheme.
Japanese Patent Publication No. 2-13372 discloses a technique of feeding reflected light back to a laser, and determining whether or not recording is properly performed based on change along a time axis of the laser-light detection signal obtained simultaneously with the recording.
However, according to the multi-pulse recording scheme described above with reference to FIG. 9C suitable for a large data recording occasion, as shown in FIG. 9E, since the luminous energy of the reflected light decreases rapidly by the interception pulse before detecting change in luminous energy of the reflected light due to the recording power, then, the luminous energy of the reflected light increases rapidly by the heating pulse applied again, and, thus, the light-emission state of the LD changes by short time intervals, it may be difficult to detect luminous-energy change for a constant power required in order to determine the formation state of a mark, and, thus, it may be difficult to properly perform controlling the power by the R-OPC.
With spread of multimedia, media only for reading such as DVD, DVD-ROM, write-once-type media such as DVD-R employing a pigment material as a recording layer, rewriteable media such as DVD-RW employing a phase-change material have been developed.
The information (sectors, in this example) recorded on such DVD media has a format as shown in FIG. 10A. According to this format, as shown in FIG. 10A, data (sectors) is continuously recorded at a fixed line density on all the tracks of the medium.
In order to prepare an information recording medium having a format having a compatibility with media for only reading, information is recorded at a frequency of a fixed recording channel clock signal while controlling the rotation speed of the medium to be inverse proportion to the track radius using a CLV (Constant Linear Velocity) scheme as shown in FIG. 10B, and, thereby, the line velocity on the track is made fixed.
However, in order to control the rotation speed of disk by the CLV scheme, to always make the line velocity on the track constant, it is necessary to change the rotation speed of the disk appropriately. For this purpose, a spindle motor which rotationally drives the disk medium should provide a large torque so as to perform velocity shift, and thus should be of a large-sized, expensive type. Moreover, as a time is required for completing a predetermined velocity shift, an extra time may be taken for accessing the disk medium as compared with HDD, MO drive, etc., for this reason.
In order to avoid necessity of rotation speed shift in recording data onto a disk medium, a recording format such as that shown in FIG. 11A may be employed. That is, as shown in FIG. 11C, the frequency of a channel clock signal to be recorded onto the disk medium is controlled as being in proportion to the radius of the track such that the frequency becomes larger as the track radius increases. Thereby, since the recording line velocity is large at the perimeter zone but is small at the central zone, as shown in FIG. 11D, the recording line density can be made fixed. It is thus possible to perform information recording on the disk medium according to a CAV (Constant Angular Velocity) scheme in which the rotation speed of the disk medium is fixed as shown in FIG. 11B.
Thereby, according to this manner, it becomes not necessary to perform control of variable rotational speed of a spindle motor which rotationally drives the disk medium, and, thus, the spindle motor should not have a large torque, and, thus, may be a small, inexpensive one. Moreover, since no rotation speed change is needed, any extra time occurring due to the velocity change is needed, and, thus, it is possible to shorten the access time needed for seeking a desired track on the disk medium.
However, the pulse width and recording power of a recording pulse series by laser light-emission for recording are optimized with respect to a specific recording line velocity for a DVD-R medium employing a pigment-made recording layer, or a phase-change medium for which, generally, a pit (mark) is formed on the disk medium at a heat mode. Therefore, the state of the mark formed or space therebetween differ at a different recording line velocity. That is, when the pulse width or recording power differ, the heat energy required for formation of a mark may vary, and, the heating temperature which can be reached varies for every mark length with respect to the optimum deformation temperature differs, and, thereby, average mark length may vary, and optimum pulse width may vary. As a result, it becomes not possible to obtain a uniform mark length, and a width of a mark may changes according to a mark length. Thus, tapering of a mark may occur (so-called tear-like mark). Thereby, the jitter characteristic may become problematic.
According to Japanese Laid-Open Patent Application No. 5-225570, in order to obtain the optimum recording luminous energy for every recordable zone of a disk medium for a short time, the optimum recording luminous energies at specific two recording line velocities are obtained at an equal recording line velocity for a trial writing zone for at least two positions, and, by performing inside or outside interpolation on the optimum recording luminous energies for two recording line velocities obtained by an interpolation routine, the optimum recording luminous energy for every recording line velocity can be obtained by performing interpolation processing on the thus-obtained optimum recording luminous energies.
According to Japanese Laid-Open Patent Application No. 5-274678, in order to reduce the laser power required for recording without worsening the jitter characteristic, recording is performed while rotating the optical disk at a uniform rotational speed, in which the light beam which has undergone intensity modulation according to the information signal based on the reference clock signals which differ for particular zones is used. Thereby, information is recorded in a zone on the perimeter side on a frequency higher than a frequency on which information is recorded in a zone on the central side. In this method, the light beam is made to have periodical pulses at a frequency which is an integral multiple of the frequency of a reference clock signal for each zone, wherein the light beam is applied to the disk medium for a zone on the perimeter side by a duty ratio of pulse-wise light emission larger than that by which the light beam is applied to the disk medium for a zone on the central side.
According to Japanese Laid-Open Patent Application No. 10-106008, in order to provide an optical disk apparatus which can perform information recording at a high velocity and with high reliability, an optical disk, an optical head, a synchronized signal generation means, a VCO, a phase comparison means, a controller, and a record signal generation means are provided, wherein recording can be performed on the best recording conditions by appropriately controlling the pulse height and pulse width of a recording signal according to a recording line velocity.
In these prior arts, the certain setting values of the recording pulses such as the duty ratio of pulse-wise light-emission are controlled according to a recording line velocity in the CAV scheme. Such a scheme is effective as long as a recording sensitivity distribution of the optical disk medium is uniform through the entire recording area of the disk, and an error of the recording power with respect to the setting value is kept constant through the entire recording area of the disk. However, for an actual disk medium, in particular, a DVD, it is difficult to perform recording uniformly through the entire recording area of the disk due to unevenness in recording sensitivity on the disk, power variation and/or wavelength variation of the LD (laser diode) due thereto.
That is, since a plurality of fluctuation factors mutually give influences on the characteristics of recorded information (RF signal), such as the jitter characteristic, it may not be possible to perform recording at a uniform signal characteristic throughout the recording area of the disk according to the above-described manners in the related art. As a result, it may not be possible to obtain the expected effects satisfactorily. Especially, in a case where the optical disk medium is concentrically divided into a plurality of recording zones, and control is made such as to interrupt and restart recording operation repeatedly across borders between different zones, so as to cope with difference in relationship between data transfer rate from a host apparatus and a data recording rate, it is difficult to perform recording at a uniform signal characteristic throughout the recording area of the disk medium.